Magnetic properties and thermal stability of Co-TM-Zr (TM=Nb, Ta, Mo, W, and Ni) amorphous sputtered films for magnetic heads

We developed a tunnel magnetoresistance (TMR) sensor consisting of a CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) and a CoFeSiB amorphous soft magnetic layer. This multilayer structure is promising for a high-sensitivity sensor because a giant TMR ratio of the MTJ and a small anisotropy field Hk of the free layer can be obtained simultaneously. However, the soft magnetic properties of the CoFeSiB layer disappear when it is annealed at above the crystallization temperature (around 300 °C), which determines the thermal tolerance of the TMR sensor and limits improvements to the sensor's sensitivity and applications. In this study, we doped the CoFeSiB layer with various amounts of Ta to raise its crystallization temperature. TMR sensors using the Ta-doped CoFeSiB layers showed thermal tolerance to annealing temperatures above 425 °C, whereas the sensor with the undoped CoFeSiB layer was tolerant to annealing temperatures up to 325 °C. As well, the Ta doping effectively reduced Hk of the CoFeSiB layer, which resulted in a sensitivity of 50%/Oe, over three times higher than the sensor with the undoped CoFeSiB layer. These results pave the way toward next-generation TMR sensors having higher sensitivity and wider applicability.

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Magnetization dynamics of soft films with thickness-dependent anisotropy

Dubuget

Thiaville

Duverger

et al. 2009

Phys. Rev. B

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The static and dynamic magnetic properties of samples consisting of two soft magnetic layers with in-plane easy axes at right angles are studied by micromagnetics and experiments. A one-dimensional micromagnetic model is developed, and solved quasianalytically for statics and dynamics. In particular, it is shown that the magnetic permeability arises from a set of eigenmodes, each with a macrospin ͑or gyromagnetic͒ response, that are excited differently depending on ac field orientation. Experiments ͑magnetization curves, permeability under field and in several directions͒ on cobalt-based amorphous alloy bilayers are well reproduced by the model with a single set of parameters. Such samples are therefore model one-dimensional nonuniform magnetic systems, simple yet with a rich behavior, for statics and dynamics.

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Magnetic properties and thermal stability of Co-TM-Zr (TM=Nb, Ta, Mo, W, and Ni) amorphous sputtered films for magnetic heads

Cited by 4 publications

References 11 publications

Two phase ferromagnetic composites in Co-Zr and Co-Zr-Fe systems containing anti-phase domain imparting very high strength

Two phase ferromagnetic composites in Co-Zr and Co-Zr-Fe systems containing anti-phase domain imparting very high strength

Enhanced sensitivity and thermal tolerance in tunnel magnetoresistance sensor using Ta-doped CoFeSiB soft magnetic layer

Magnetization dynamics of soft films with thickness-dependent anisotropy

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